It is proposed to purify ornithine-gamma-aminotransferase as a single protein component from rat liver, rat kidney and Chang's liver cells, a transformed cell line in culture. The purified enzymes will be compared with respect to kinetics, physico-chemical properties, molecular and sub-unit structure. It is aimed to relate the differences in molecular structure and functional properties to the differences in the control and regulation of turnover of these three (or more) proteins and to develop a foundation for understanding of the control of gene expression that must be reflected in these processes during differentiation, development, transformation and neoplasia.